The invention relates to a track roller, in particular a bottom roller, for crawler vehicles; its field of application, however, also embraces top roller and tensioning roller functions.
The prior art teaches bottom rollers for the tracks of crawler tractors and similar vehicles, which comprise a shaft, fixed immovably to the main body of the vehicle and carrying the actual roller component, the latter rotating idle about the fixed shaft.
The roller itself is fashioned from suitably heat-treated steel, and is provided with appropriate cylindrical contact surfaces by way of which it is able to roll against the track links. Rims are also provided by means of which to keep the track correcly aligned when rolling.
The roller is hollow, and when paired with the shaft creates a chamber designed to contain a permanent supply of lubricant.
Rolling bearings enable the roller to rotate about its fixed shaft, and may be either of the ball or of the roller type. Such bearings absorb both radial load and axial thrust produced once the track is in motion, and are seated in special recesses at either end of the roller, the outer race of each bearing being pressed into a relative recess, thus turning as one with the roller. Means are provided, in the shape of a shoulder located at the inside of each recess, by which to prevent either bearing from shifting in an axial direction toward the center of the roller.
Thrust-brackets pressed onto the shaft, and therefore integral with the latter, abut with the inner race of the bearing at each respective end of the roller, and serve to prevent end float of either of the two bearings.
Thus, the bearings roll in a fixed axial position, lodged between the shoulders of the roller on the one hand, and the shaft thrust-brackets on the other; the roller in its turn remaining fast between its bearings and unable to move in an axial direction.
Seeing that the bearings are in direct contact with the lubricant chamber, means must be provided by which to prevent egress of the lubricant, and these take the form of conventional O-rings located between the shaft and the fixed thrust-bracket inner surfaces. Fluid is therefore prevented from seeping out along the shaft. Further seals are provided between the track-roller's bearing recesses and their respective adjacent thrust-brackets, which perform the dual function of preventing egress of lubricant by way of the bearings, and of excluding dust and dirt which would be damaging to the latter.
In track-rollers according to the prior art, these last-mentioned seals each take the form, substantially, of a pair of opposed annular metallic elements. Such opposed elements make direct contact one with the other, the first such element integral with the thrust-bracket, hence with the shaft, and the second integral with the track-roller. At least one thrust washer is located between the thrust-bracket and the first annular element, and will be fashioned from, for instance, an elastomer material. The annular elements thus arranged are permitted a slight degree of axial movement, and the fixed thrust-bracket urges them one against the other continually.
The actual contact surfaces which provide the seal are incorporated into the annular elements themselves, and take the form of accurately machined radial edges breasted together in relative rotation.
The thrust-brackets also incorporate a tubular body extending as far as the relative free end of the fixed shaft and offering the appropriate fitting by way of which the bracket itself may be mounted to the body of the vehicle; for it will be appreciated, as the shaft of the track-roller is immovably fixed to these brackets, the brackets themselves afford the means by which the shaft may be secured to the body of the vehicle.
The invention described herein sets out to improve track-rollers of the type thus briefly outlined, and in particular, seeks to simplify and reduce the cost of manufacture, whilst up-grading performance.